Recently, because of the fact that ink-jet recording methods produce images simply and at low cost, they have been applied to various printing fields such as photography, various kinds of printing, and special printing jobs such as marking and production of color filter. Specifically, for the recording apparatus by which fine dots are ejected and controlled, ink whose color reproduction area, durability, and ejecting property are improved, and an exclusive use sheet in which the absorbability of the ink, coloring property of the coloring material, surface glossiness are greatly increased, are used, and the image quality comparative to silver halide photography can be obtained. The increase of the image quality of today's ink-jet recording system is achieved only when a state of the art recording apparatus, ink, and exclusive use sheet are present.
However, in the ink-jet system for which an exclusive use sheet is necessary, the recording medium is limited and the increased cost of the recording medium becomes a factor. Accordingly, many trials to record onto the transferred medium other than exclusive use sheets by the ink-jet system have been made. Specifically, a phase change ink-jet system in which a solid wax ink, being solid at room temperature, is used, a solvent series ink-jet system in which the ink in which a quick dry type organic solvent is a main component, is used, or an ultraviolet ink-jet system in which, after the recording, a cross-linkage is formed by exposure to ultra violet (UV) rays.
Among the above-mentioned experiments, the UV ink-jet system has a relatively low odious smell comparing to the solvent series ink-jet system, and for its strong point in that it can record onto recording media not featuring a quick dry property and ink absorbability, it has been noted recently. Listed as examples are, for example, JP-B (hereinafter, the term JP-B referrers to an examined Japanese Patent Publication) 5-54667, JP-A (hereinafter, the term JP-A refers to a Japanese Patent Application Publication) 6-200204, and Japanese Translated PCT Patent Publication No. 2000-504778, in which an ultraviolet curing type ink-jet ink is disclosed.
As mentioned above, the ink-jet image forming method using ultraviolet curing ink, being different from the existing ink-jet system using water-based ink, is expected to be practically applied to non-absorptive media such as plastic film, since better images can be obtained even without an ink absorbing layer in the recording medium. The ultraviolet curing type ink is prepared with radical polymerization or cationic polymerization. Cationic polymerization type ink is not affected by polymerization inhibition by oxygen, resulting in a quite advantageous technology to achieve high sensitivity in an image forming method using ink-jet ink droplets having a large specific surface area. However, it also has drawbacks such as having a tendency to be affected by the atmosphere at the time of image recording, such as ambient temperature and humidity.
To overcome the foregoing drawbacks, proposed has been a method to enhance acceleration of the ink hardening rate by provision of a deposited ink heating means (for example, ref. Patent Document 1). However, in cases when the foregoing method is applied to methods which supply a large amount of ink at once onto the recording medium, such as a so-called serial printer with reduced interleaves, or a printer using a line head, the balance of hardening between the recording medium surface and the rear surface is lost when cured by ultraviolet rays, specifically in high humidity conditions, resulting in lowered scratch resistance of formed images, or problems of causing cracks on the image surface when bent. Therefore, the present situation is urgent development of an improved solution is desired.
Patent Document 1: JP-A 2002-137375 (claims)